Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F9/00—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium
  • F16F9/32—Details
  • F16F9/53—Means for adjusting damping characteristics by varying fluid viscosity, e.g. electromagnetically
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F9/00—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium
  • F16F9/10—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium using liquid only; using a fluid of which the nature is immaterial
  • F16F9/14—Devices with one or more members, e.g. pistons, vanes, moving to and fro in chambers and using throttling effect
  • F16F9/16—Devices with one or more members, e.g. pistons, vanes, moving to and fro in chambers and using throttling effect involving only straight-line movement of the effective parts
  • F16F9/18—Devices with one or more members, e.g. pistons, vanes, moving to and fro in chambers and using throttling effect involving only straight-line movement of the effective parts with a closed cylinder and a piston separating two or more working spaces therein

Definitions

• Controllable dampers for vehicles are knc in which, for example, two or more hydraulic cylinder dampers ar 'switched' in parallel to control the stiffness according to detected vibration frequency.
• a convenient method of doing this is to use a single cylinder with two or more orifices which are opened and closed as the conditions require.
• dampers In railway vehicles particularly, there is a demand for dampers with a very high operating speed and it is found that known controllable dampers are not satisfactory in this respect. Additionally, dampers such as described above have a step change control and in many application continuous control is highly desirable.
• One object of the present invention therefore is to provide a continuously controllable motion damper with a very high operating speed.
• a controllable motion damper comprises a volume of damping fluid contained within two flexible envelopes connected by a nozzle, the two envelopes being externally subject to differential pressure resulting in operation from differential movement between members linked by the damper, the differential pressure causing the damping fluid to be forced
• the damping fluid being a suspension of low coercivity magnetic particles
• electromagnetic means being provided for producing a controllable magnetic field within the nozzle to control the viscosity of the damping fluid.
• viscosity of the magnetic suspension is not to the classical viscosity of the fluid; it is rather to the 'stiffness' or 'strength* resulting from the inclination of the magnetic particles to conform to the field pattern. It should be understood that in this specification it is this 'non-Newtonian viscosity' that is referred to.
• each section of the nozzle diverges continuously with a taper angle between 5° and 20° and preferably in the region of 10°.
• the envelopes may be of compressible bellows form.
• Each of the envelopes may be enclosed in a respective inexpansible enclosure containing hydraulic fluid between the envelope and the enclosure wall, the two enclosures being connected to a source of differential pressure so that as hydraulic fluid is pumped into one enclosure in operation the enclosed envelope is compressed to cause the damping fluid to pass through the nozzle.
• the two enclosures may be provided by a single cylinder having a partition through which the nozzle extends.
• the source of differential pressure may comprise a master cylinder having a double action piston, connections to the enclosures being taken from the master cylinder on each side of the piston, the piston being adapted for connection as a link between the damped members.
• the envelopes may be mounted in respective inexpansible enclosures having a common wall through which the nozzle extends, the enclosures together forming a common piston in a cylindrical housing, each enclosure being open to a respective end of the cylindrical housing, the enclosures and housing being
• the bore of the nozzle may be grooved axially so that a cross section of the bore exhibits a corrugated wall.
• a damper according to any preceding claim wherein the bore of the nozzle has at least a lining of mechanically refractory material for resisting erosion by passage of the damping fluid.
• the electromagnetic means may comprise a coil wound around the nozzle at least in the region of the minimum common cross-section.
• the coil extends along the nozzle between positions within the length of the nozzle.
• Fi gure 1 is a diagram of a central feature of the damper, ie a nozzle l imiting the fl ow of dampi ng flud;
• Fi gure 2 i s a diagram of the mai n features of one embodiment of damper ;
• Figure 3 i s a diagram of an alternati ve embodiment
• Figure 4 i s a diagram of a cross secti on of a modi fied version of the nozzle of Fi gure 1.
• Fi gure 1 of the drawings shows , very diagram ati cal ly, a damping nozzle 1 and part of the associated apparatus .
• the nozzl e 1 consi sts of a cerami c cyl inder havi ng a double conical bore whi ch di verges in both di recti ons f rom the central minimum common cross -section 3 with a total taper angl e of approximately 10°.
• the central part of the nozzle i s wrapped with a coil 5 such as , when energised, to produce an axial magnetic fiel d in the nozzle bore.
• a flexible envelope 7 is connected, this being formed from a durable rubber-type material.
• the envelope 7 has a wall of bellows form to permit a change in volume of the envelope.
• the space contained by the two bellows and the nozzle is filled completely with a damping fluid 9 which consists of a suspension of soft-iron particles in oil or hydraulic brake fluid.
• the particles need to be sufficiently small and spherical that t ey do not pack hard when left standing for long periods. While soft-iron is a common and cheap material, other magnetic materials will be suitable if they are of sufficiently low coercivity. When the current is removed from the coil 5 it is required that the particles become substantially de-magnetised.
• FIG 2 shows one convenient arrangement for operating the damper of Figure 1.
• the two envelopes 7 are mounted in a cylinder 11 which has a central partition 13 sealed to and supporting the central nozzle assembly of nozzle 1 and coil 5.
• Two enclosures 8 and 10 are thus formed, each of which encloses one of the envelopes 7.
• the cylinder 11 is closed but for two pipe connections 15,17 to a piston cylinder 19.
• the two cylinders 11 and 19 are completely full of hydraulic fluid as used for example, in fluid drive systems. There may in practice be a reservoir and a non-return valve, not shown.
• the piston 21 is mounted on a piston rod 23 which extends through sliding seals in the cylinder 19 in both directions. The total volume of fluid contained in the cylinder 19 is therefore unchanged as the piston moves since there is always the same volume of rod 23 within the cylinder 19.
• the piston rod 23 has
• SUB one end coupling 25 adapted for coupling to one of two parts of a vehicle which in operation move relatively to each other with varying degrees of shock.
• the cylinder 19 has a fixed coupling 27 (shown very diagrammatically), which couples to the other of these two relatively movable parts.
• the piston rod coupling 25 would couple to the bogie, say, and the cylinder coupling 27 to the carriage body.
• the nozzle 1 there is an inherent resistance to flow due to the restricted orifice, having a minimum cross-section 3.
• This resistance can, however, be increased very considerably by creation of the magnetic field previously referred to.
• the coil current is increased at a rate, and to a value, determined in a feedback loop.
• the magnetic particles in the damper fluid 9 tend to cling together so that what was previously a fairly free flowing fluid becomes a viscous semi -liquid.
• the force resisting the shock movement increases with the velocity of the movement but also increases fairly linearly with the magnetising current. With minimal inductance the current and therefore the magnetic field and the damping force can be
• the bore of the nozzle is tapered at not too shallow an angle. 30° (total) taper angle is a reasonable minimum although the disadvantageous effect now to be described will occur to a greater and lesser extent as this angle is decreased and increased respectively.
• a further improvement is made by restricting the coil length to less than that of the nozzle so that there is a portion of damping fluid at the ends of the nozzle not enclosed by the coil and which is therefore subjected to magnetic field of smaller intensity.
• the effect of these two modifications is to grade the transition between the more nearly solid damping 'fluid' in the nozzle and the more liquid fluid in the envelope 7.
• a highly efficient smoothly controllable damper is thus provided having a very rapid response to shock movements and to the application of control current.
• the nozzle is totally of ceramic to provide an erosion resistant bore to the nozzle, other refractory materials may be used, even non magnetic low conductivity metal alloys.
• a further modification is to use a nozzle having suitable magnetic and conductive characteristics but merely coated with refractory material. It will be clear of course that a damping fluid carrying iron particles, in suspension will be very erosive. It is for this reason that the damping fluid is isolated from any sliding surface in the described
• the 'master' cylinder 19 can be positioned suitably for the members to be damped, while the damping cylinder 11 can be positioned remotely.
• the pipes 15 and 17 may be rigid or flexible.
• the whole arrangement is incorporated in a single cylinder 29.
• This acts in the same manner as the master cylinder of Figure 2, the cylinder itself being coupled (27) to one of the damped members and the piston rod 23 being coupled (25) to the other.
• the piston 31 is closely similar to the 'slave' unit 11 of Figure 2.
• the cylinder 31 carries the damping unit 1, 7 and 7 mounted on a partition 13 which divides the cylinder 31 into two enclosures. In this case however, the two enclosures are open at vents 33 into the master cylinder 29.
• the cylinder 31 is slidable within cylinder 29, being sealed by 0-ring 35 to separate the hydraulic fluid in the two ends of the master cylinder.
• the tapered bore is corrugated, as shown in Figure 4. Again this tends to inhibit the formation of a magnetic plug of damping fluid when the semi-solidified fluid is forced out of the nozzle.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Fluid-Damping Devices (AREA)
• Vehicle Body Suspensions (AREA)
• Buildings Adapted To Withstand Abnormal External Influences (AREA)
• Vibration Prevention Devices (AREA)
• Valve-Gear Or Valve Arrangements (AREA)
• Oscillators With Electromechanical Resonators (AREA)
• Valve Device For Special Equipments (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10717232

Family Applications (1)

Country Status (7)

Cited By (1)

Families Citing this family (18)

Citations (5)

Family Cites Families (1)

• 1992
  • 1992-06-17 GB GB9212821A patent/GB2267947B/en not_active Expired - Fee Related
• 1993
  • 1993-06-16 AT AT93913375T patent/ATE131914T1/de not_active IP Right Cessation
  • 1993-06-16 DK DK93913375.7T patent/DK0598098T3/da active
  • 1993-06-16 ES ES93913375T patent/ES2081219T3/es not_active Expired - Lifetime
  • 1993-06-16 EP EP93913375A patent/EP0598098B1/en not_active Expired - Lifetime
  • 1993-06-16 DE DE69301084T patent/DE69301084T2/de not_active Expired - Fee Related
  • 1993-06-16 WO PCT/GB1993/001274 patent/WO1993025827A1/en active IP Right Grant

Patent Citations (5)

Non-Patent Citations (3)

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